The present invention relates to telecommunication systems. In particular, the invention concerns a new type of method and system for implementing intermediary services.
xe2x80x98Virtual Private Networkxe2x80x99 (VPN) means a network that allows the transmission of private communications using the resources of the Public Switched Telephone Network (PSTN). In this way, it is possible to interconnect company offices geographically situated in different areas. Offices can also be connected to each other using semifixed lines. However, this alternative is less effective and more expensive than the first mentioned one.
Using a virtual private network, it is possible to interconnect Centrex subscriber groups, Public Branch Exchanges (PBX) and individual subscribers. xe2x80x98Centrex subscriber groupxe2x80x99 refers to a subscriber group that, without being connected to a separate public branch exchange, can utilize functions typical of extensions connected to one. These functions are to be understood as referring to the services produced by a public branch exchange, e.g. services such as Call Hold and Three Party Service. A Centrex subscriber group is so implemented in a telephone switching center that the switching center will provide services like those of a public branch exchange or PBX network, yet without separate public branch exchanges.
A feature typical of the functions of a virtual private network is a private numbering plan. This is a telecommunication service that allows the subscriber to use subscriber numbers deviating from the public numbering plan for communication between certain subscriptions within the area of one or more networks. A numbering plan can be implemented e.g. by reserving subscriber numbers beginning with a given combination of digits for use by a company or a similar community. Correspondingly, a separate billing system can be introduced in a VPN network. It is possible to define lower rates to be charged for internal calls within the VPN network than for outgoing calls from the VPN network.
A telephone exchange supporting the VPN service is provided with a special database in which are stored all the numbers included in the public numbering plan that correspond to the private numbering plan. The VPN service can be extended so as to allow it to be used between several telephone exchanges. This may be so implemented that a corresponding database is provided in each exchange. In the signalling between two VPN exchanges, a number included in a private numbering plan is converted into a number included in the public numbering plan. The subscriber, which may be e.g. an analog subscriber, an ISDN subscriber (ISDN, Integrated Services Digital Network) or a branch exchange, dials the numbers and the public network exchange performs the number conversion. If the subscriber dials a number included in a private numbering plan, then the public network exchange will convert the number into a number consistent with the public numbering plan. In other words, the public telephone network uses numbers consistent with the public numbering plan, which are converted in VPN exchanges so that the users of terminal equipment will see the numbers consistent with the private numbering plan. Each client may have a different numbering plan. A VPN network is always a client-specific network and therefore the network is configured so as to meet the needs of the client.
In a virtual private network, it is possible to use signalling consistent with the QSIG standard. QSIG is ISDN common channel signalling designed for use in private networks. The QSIG signalling was developed by an open group of companies comprising all of the largest European manufacturers of branch exchanges. The abbreviation QSIG refers to signalling transmitted over an ISDN Q-point. The Q-point is a logical signalling point between two PINX""s (PINX, Private Integrated services Network exchange). QSIG defines a number of protocols which can be used for interaction between a plurality of PINX""s. A PINX is connected to the nearest telephone exchange e.g. via a 2 Mbit/s link used to carry QSIG signalling. A QSIG protocol largely resembles the ITU-T (International Telecommunication Union) Q.931 protocol. The essential difference between these is that Q.931 is an asymmetric protocol while QSIG is symmetric.
A PBX-network intermediary generally works under one of the main PBX""s. In this context, xe2x80x98intermediaryxe2x80x99 refers e.g. to a telephone set equipped for intermediary services or to a computer provided with facilities for intermediary services. The concept of xe2x80x98intermediaryxe2x80x99 may further comprise a human user of the above-mentioned equipment. Furthermore, in VPN it is possible to centralize intermediary services by building a fixed connection between the intermediary and the branch exchange. In this case, one intermediary can only serve one network at a time. However, this solution involves problems regarding load distribution and routing. The services produced by an intermediary include e.g. CLIP/CLIR (CLIP, Calling Line Identification Presentation; CLIR, Calling Line Identification Restriction), COLP/COLR (COLP, Connected Line Identification Presentation; COLR, Connected Line Identification Restriction), Call transfer, Call offer, Call intrusion and Common information.
The object of the present invention is to eliminate the drawbacks referred to above or at least to significantly alleviate them. A specific object of the invention is to disclose a new type of method and system for implementing intermediary services. In the method, an intermediary in a virtual private network is centralized in a public network exchange. When e.g. the standardized signalling for a QSIG branch exchange network is used, the intermediary can use the same services that would be possible if the intermediary were connected directly to a branch exchange.
As for the features characteristic of the present invention, reference is made to the claims.
The method of the invention concerns the implementation of a centralized intermediary service in a telecommunication system. The telecommunication system of the invention comprises a telephone network, preferably an ISDN network. The telephone network comprises one or more telephone exchanges. However, ISDN network is only an example of telephone networks applicable. Implemented in the telephone network is a Private Numbering Plan (PNP), allowing the use of abbreviated numbers within the network. The system further comprises a telephone exchange forming part of the telephone network and implementing the private numbering plan. The telephone exchange comprises a readiness for implementing VPN services. Moreover, the system of the invention comprises an intermediary which takes care of communication in the VPN network.
In the method, one or more virtual private networks are created in the telecommunication system and a private numbering plan established is used for internal calls in the virtual private network. According to the invention, the intermediary is logically connected to the telephone exchange and the signalling of the virtual private network is used for the production of intermediary services. Intermediary services are produced using e.g. QSIG signalling. The signalling used may alternatively be DPNSS (DPNSS, Digital Private Network Signalling System), DSS1+ (DSS, Digital Subscriber Signalling System) or some other signalling. DPNSS is a protocol developed by British Telecom and PINX manufacturers. The DSS1+ protocol is defined in ETSI (European Telecommunication Standardization Institute) standards EN 301 060-1 and EN 301 061-1.
In a preferred embodiment, the intermediary is connected to one or more virtual private networks. For each virtual private network, a separate private numbering plan can be defined. When a call is being set up, the signalling message contains data indicating which virtual private network the subscriber belongs to. Thus it is possible to identify the numbering plan being used. The telephone exchange performs the number conversion between the internal numbering of the private network and the public numbering plan.
In a preferred embodiment of the invention, a numbering table enabling the provision of centralized intermediary services is implemented in the telephone exchange and/or intermediary.
In a preferred embodiment of the invention, the telephone network is connected to an Intelligent Network (IN) and a numbering table enabling the provision of centralized intermediary services is implemented in a database in the intelligent network.
In a preferred embodiment of the invention, internal signalling within the telephone network is implemented using an ISUP protocol (ISUP, ISDN User Part). Messages related to a virtual private network are transmitted e.g. by encapsulating them inside ISUP messages. In this way, it is possible to implement a transparency of message traffic within the public telephone network.
In the system of the present invention, the intermediary is connected to a telephone exchange. The system comprises means for using the signalling of a virtual private network for the production of intermediary services.
In a preferred embodiment of the invention, the system comprises means for using QSIG signalling for the production of intermediary services.
In a preferred embodiment of the invention, the system comprises means for using DPNSS signalling for the production of intermediary services.
In a preferred embodiment of the invention, the system comprises means for using DSS1+ signalling for the production of intermediary services.
In a preferred embodiment of the invention, the system comprises means for serving one or more virtual private networks and a numbering table enabling the provision of centralized intermediary services.
In a preferred embodiment of the invention, the system comprises an intelligent network connected to the telephone network and, located in a database in the intelligent network, a numbering table enabling the provision of centralized intermediary services.
In a preferred embodiment of the invention, the system comprises an ISUP protocol used for internal signalling within the telephone network.
The invention makes it possible for an intermediary to produce the same services that would be possible if it were connected directly to a private branch exchange. In addition, the invention makes it possible for a single intermediary to serve several VPN networks simultaneously. Furthermore, the invention makes it possible for a single intermediary to serve several VPN networks, i.e. several enterprises, via the same user interface. The invention also makes it easier for the operator to centralize services and distribute resources.